Re: [PATCH net 7/9] net/mlx5e: Properly access RCU protected qdisc_sleeping variable

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 10 Jun 2025 18:15:12 +0300 Mark Bloch wrote:
> qdisc_sleeping variable is declared as "struct Qdisc __rcu" and
> as such needs proper annotation while accessing it.
> 
> Without rtnl_dereference(), the following error is generated by smatch:

sparse ?

> 
> drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40: warning:
>   incorrect type in initializer (different address spaces)
> drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40:    expected
>   struct Qdisc *qdisc
> drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40:    got struct
>   Qdisc [noderef] __rcu *qdisc_sleeping
> 
> Fixes: 214baf22870c ("net/mlx5e: Support HTB offload")

I don't think this is a functional change? We don't treat silencing
compiler warnings as fixes, not for sparse or W=1 warnings.

> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
> Signed-off-by: Mark Bloch <mbloch@nvidia.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en/qos.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
> index f0744a45db92..2f32111210f8 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
> @@ -374,7 +374,9 @@ void mlx5e_reactivate_qos_sq(struct mlx5e_priv *priv, u16 qid, struct netdev_que
>  void mlx5e_reset_qdisc(struct net_device *dev, u16 qid)
>  {
>  	struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, qid);
> -	struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
> +	struct Qdisc *qdisc;
> +
> +	qdisc = rtnl_dereference(dev_queue->qdisc_sleeping);
>  
>  	if (!qdisc)

nit: no new line between action and error check